In the treatment of industrial wastewaters, application of two or more than one methods is required in many cases. Electrocoagulation (EC) is capable of producing the metal hydroxide flocs in sewage to be cleaned by electro dissolution of anode and membrane bioreactor (MBR) is capable of producing high quality effluents. Therefore, the combining of these two methods compared to the single treatment methods, leads to a higher removal efficiency. In this study, the efficiency of EC in treatment of baker’s yeast wastewater with Aluminum electrodes was evaluated. Effect of operating parameters including current density, electrolysis time and pH on the removal efficiency of COD and turbidity were evaluated. In the EC process, COD and turbidity of influent from 9500 mg/L and 2700 NTU reduced to 4000 mg/L and 273 NTU respectively and the maximum removal efficiency of COD and turbidity were 58% and 90% respectively. As the result of optimization, the maximum removal efficiency of COD and turbidity at optimal conditions of 19 mA/cm 2 current density, 38.8 min electrolysis time and pH 5.5 were 52% and 89%, respectively. Then the pretreated wastewater with EC was fed to the MBR whitch has been adapted with baker’s yeast wastewater. Physical and chemical analysis such as COD, BOD and turbidity were measured during the process. In MBR process, in a 26 days operation, COD, BOD and turbidity of influent from 4000 mg/L, 1011 mg/L and 289 NTU reduced to 1229 mg/L, 253 mg/L and 2.72 NTU respectively and the maximum removal efficiency of COD, BOD and turbidity for pretreated feed with EC were 70%, 75% and 99%, respectively. In this period, COD of mixed liquor in the reactor was also measured regularly and the maximum removal efficiency of COD for biological treatment of the reactor (without presence of membrane) was 65% and the difference between COD of mixed liquor and permeate effluent was 4% averagely that is showing the advantage of MBR process than conventional activated sludge process in treatment of wastewater. The average of organic loading rate of the bioreactor was 3.1 kg COD/m 3 .day. Concentrations of MLSS in the bioreactor were between 2900-6800 mg/L. HRT was set to 24 hr theoretically. In combined process of EC-MBR the maximum removal efficiency of COD and turbidity of baker’s yeast wastewater were 87% and 99.9%, respectively, that is showing the advantages of the combined methods of wastewater treatment. Keywords : Electro Coagulation, Response Surface Method, Membrane Bioreactor, Baker’s Yeast Wastewater, Combined Methods of Wastewater Treatment
